Source : Free On-Line Dictionary of Computing

digital signature
     
         Extra data appended to a message which
        identifies and authenticates the sender and message data using
        {public-key encryption}.
     
        The sender uses a {one-way hash function} to generate a
        hash-code of about 32 bits from the message data.  He then
        encrypts the hash-code with his private key.  The receiver
        recomputes the hash-code from the data and decrypts the
        received hash with the sender's public key.  If the two
        hash-codes are equal, the receiver can be sure that data has
        not been corrupted and that it came from the given sender.
     
        (1995-02-07)